As it is well known feedback can enlarge the capacity region of MAC by inducing statistical cooperation between the transmitters [1]}. Consider
the following two-user additive Gaussian noise MAC with feedback,
\(Y_i = \sqrt{\gamma _i } X_{\left( 1 \right)i} + \sqrt{\gamma _i } X_{\left( 2 \right)i} + W_i ;\;\;i \in \left[ {1:n} \right]\) 
